Camomile, the dried flower heads of Matricicaria chamomilla L., Compositae, and/or Anthemis nobilis L., Compositae, contains a number of commercially useful aromatic substances, fragrances, and medicinal products which are very sensitive to even mildly elevated temperatures. For example, when camomile tea is prepared in the home by pouring hot water over the dried flower heads, the resulting tea contains only a fraction of those substances originally present in the camomile, the rest having been destroyed by heat. Furthermore, some of the substances present in the tea have low solubility in water so that a significant portion of these substances will remain in the flower heads. Accordingly, the use of warm or hot water as an extraction solvent for commercial use is not feasible.
When organic solvents are used as the extraction medium for camomile, a number of disadvantages result. For example, traces of the organic solvents will remain in the extract, and are almost impossible to separate quantitatively from the extract.
One prior art method used to recover camomile substances using a milder extraction procedure is disclosed in German Patent DE-OS No. 27 09 033, wherein a non-toxic gas such as carbon dioxide, with the gas in the supercritical state, is used to extract the camomile. However, where supercritical gases are used, a temperature above the critical temperature of the gas must be employed. When carbon dioxide is the gas selected, the temperature must be maintained above 31.06.degree. C., which is its critical temperature. Supercritical gas was chosen in that process since in the supercritical state both the density of the gas and solubility of substances in the gas can be considerably increased when high extraction pressures are used. However, due to the extreme sensitivity to even slightly elevated temperatures of some of the substances in camomile, particularly proazulenes such as matricin, this prior art extraction method is not without its drawbacks.
Liquid carbon dioxide has been used in certain prior art extraction processes. A survey of the state of the art can be found in W. G. Schultz et al. in "Food Technology", Vol. 24, 1282 et seg, (1970) and Vol. 28, 32 et seg. (1974). As can be seen from these literature references, extractions with liquid carbon dioxide are used for coffee, spices, and to extract aromatic substances from fruits. German Patent DE-AS No. 28 27 002 discloses an extraction process using liquid carbon dioxide for hops. However, for the extraction of camomile, only the above-mentioned process using supercritical carbon dioxide is known.